1. Field of the Invention
The present invention relates to a zoom lens and an image pickup apparatus including the zoom lens, which are particularly suitable for use in a broadcasting television camera, a cinema camera, a video camera, a digital still camera, and a silver-halide film camera.
2. Description of the Related Art
In recent years, a small and lightweight zoom lens having a wider angle of view, a higher zooming ratio, and higher optical performance is required for an image pickup apparatus such as a television camera, a cinema camera, a film camera, or a video camera. In particular, image pickup devices such as a CCD and a CMOS, which are used in the television or cinema camera as a professional video photographing system, have a substantially uniform resolution over the entire image pickup range. Therefore, the zoom lens using the image pickup device is required to have a substantially uniform resolution from a center to a periphery of the screen. Further, reduction in size and weight is also required for photographing modes that put a high priority on mobility and operability.
As a zoom lens having a wide angle of view and a high zooming ratio, there is known a positive-lead type five-unit zoom lens including five lens units as a whole, in which a lens unit having a positive refractive power is arranged at the end on an object side.
In Japanese Patent Application Laid-Open No. 2011-81065, there is disclosed a five-unit zoom lens including, in order from the object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having the positive refractive power, a fourth lens unit having the negative refractive power, and a fifth lens unit having the positive refractive power. In Japanese Patent Application Laid-Open No. H10-31157, it is disclosed that the change in interval between the second lens unit and the third lens unit is defined for the purpose of aberration correction. In Japanese Patent Application Laid-Open No. 2011-81065, it is disclosed that the change in interval between the second lens unit and the third lens unit is defined for the purpose of reducing the size and weight of the first lens unit.